Question

In the circuit given below, the switch is closed at time t=0. The voltage across the inductance just at t=0^+ is ____________

(a) 2 V

(b) 4 V

(c) -6 V

(d) 8 V

This question was addressed to me during an interview.

The above asked question is from Dot Convention in Magnetically Coupled Circuits topic in chapter Resonance & Magnetically Coupled Circuit of Network Theory

Answer 1

Correct answer is (b) 4 V

To elaborate: A t=0^+,

I (0^+) = \(\frac{10}{4||4+3} = \frac{10}{5}\) = 2A

∴ I2(0^+) = \(\frac{2}{2}\) = 1A

VL(0^+) = 1 × 4 = 4 V.